I$\text{'}$m having a little trouble on my computer science homework. Our professor provided us with the outline of some code that we have to complete and I$\text{'}$m having trouble figuring out how to do some of them. Here is a segment I was working that was giving me trouble:

import java.util.ArrayList;

public class BinarySearchTree $\{$

Node root;

public BinarySearchTree$()\{$

this.root $=$ null;

$\}$

public BinarySearchTree$($Node p$)\{$

this.root $=$ p;

$\}$

public boolean isEmpty$()\{$

$/**$

$*$ check if the tree is empty

$*$ @return true for yes, false for no

$*/$

$\}$

public boolean isValid$($Node start$)\{$

$/**$

$*$ Given a binary tree, check if the tree is a binary search Tree

$*$ @return true for yes, false for no

$*/$

$/**$

$*$ if the node element is greater than leftchild and smaller than rightchild,

$*$ recursively check if its leftsubtree and rightsubtree are binary search tree

$*/$

$\}$

public boolean setRoot$($Integer e$)\{$

$/**$

$*$ if tree does not have a root, create root node using e and return true, otherwise, return false

$*/$

$\}$

public int size$($Node start$)\{$

$/**$

$*$ count and return the number of nodes in the tree rooted at start

$*/$

$\}$

public int depth$($Node target$)\{$

$/**$

$*$ count and return the depth of node target

$*/$

$\}$

public int height$($Node start$)\{$

$/**$

$*$ find and return the height of tree or subtree rooted at start

$*/$

$\}$

public Node parent$($Node start, Node target, Node parent$)\{$

$/**$

$*$ Given a tree or subtree rooted at start, find the target node and return its parent

$*/$

$/*$recursion

$*$ if target is root, return base case

$*$ if start is null, return null

$*$ if start is target, return parent

$*$ if target element is smaller than start element, find parent on left subtree

$*$ if target element is greater than start element, find parent on right subtree

$*$

$**/$

$\}$

public int numChildren$($Node target$)\{$

$/**$

$*$ return the number of children for the node referred by target

$*/$

$\}$

public boolean isInternal$($Node target$)\{$

$/**$

$*$ check if a node target is an Internal node, return true for yes, false for No

$*/$

$\}$

public boolean isExternal$($Node target$)\{$

$/**$

$*$ check if a node target is an external node, return true for yes, false for No

$*/$

$\}$